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November 1951 E-830 

United States Department of Agriculture 

Agricultural Research Administration 

Bureau of Entomology and Plant Quarantine 



DETERMINING THE EFFICIENCY OF RESPIRATORY CARTRIDGES 
AND GAS-MASK CANISTERS AGAINST DUSTS AND SPRAYS 

By R. A. Fulton and M. S. Konecky, Division of Insecticide Investigations, 
and Floyd F. Smith, Division of Truck Crop and Garden Insect Investi- 
gations 



Concern over the inhalation hazard to operators applying dusts, sprays, 
and aerosols of parathion and other organic -phosphorus insecticides led to 
a conference, in September 1949, by representatives of several govern- 
ment agencies, and to subsequent meetings with producers of these in- 
secticides and of respiratory protective devices. A cooperative program 
was set up, under the auspices of the Interdepartmental Committee on 
Pest Control for the development of respirators and gas masks for the 
protection of operators while handling these materials. Experimental 
models of respirators, respirator cartridges, and gas-mask canisters 
were supplied by the manufacturers. Testing procedures to determine 
their efficiency were developed and applied by chemists of the Bureau of 
Entomology and Plant Quarantine, and the results were evaluated jointly 
by the Department of the Army, Food and Drug Administration, Public 
Health Service, Bureau of Mines, Production and Marketing Administra- 
tion, and Bureau of Entomology and Plant Quarantine. Various types of 
cartridges and canisters were tested against parathion and other organic - 
phosphorus insecticides and also against dieldrin, aldrin, and chlordane. 

As a result of this investigation respirator cartridges that contain 
a special dust filter have been developed and are now being sold for 
protection against parathion dusts and sprays (Fulton 1). More recently 
the same units have also been found effective against dieldrin, aldrin, 
and chlordane. They are not effective against tetraethyl pyrophosphate, 
but other units have been developed for that purpose (Fulton, Nelson, 
and Smith 2). 

On May 4, 1950, the Interdepartmental Committee on Pest Control 
issued a statement concerning these respirators, and listed several 
commercial respirators that have been found to give such protection. 
A similar statement concerning devices that will give protection against 
dieldrin, aldrin, and chlordane was issued by the Bureau of Entomology 
and Plant Quarantine on August 24, 1951. The methods used for EPN and 
nicotine are similar to those described for parathion and tetraethyl 
pyrophosphate. 



2- 



Test Insects 



The chrysanthemum aphid ( Macrosiphoniella sanborni (Gill.)), the 
foxglove aphid ( Myzus convolvuli (Kltb.)), and parathion-resistant and 
nonresistant strains of the two-spotted spider mite ( Tetranychus 
bimaculatus Harvey) were used as test insects. 

The chrysanthemum aphid was reared on young chrysanthemum plants 
in active growth, and the foxglove aphid was reared on potato leaves. 
The tip of each shoot was removed, and the upper part of the stem was 
coated with paraffin to force the aphids to feed on the lower expanded 
leaves. The two strains of the two-spotted spider mite were reared on 
potted lima bean plants in separate sections of a greenhouse. The 
varieties Carolina Sieva and Henderson Bush were used, because they 
are highly resistant to mildew and have relatively small leaves. 

Tests of Respirator Cartridges 

Apparatus, --The apparatus for testing respirator cartridges is shown 
in figure 1. It consists essentially of a dusting or spraying chamber (A), 
a cartridge holder (D), a chamber for exposing the test insects (E), a 
flowmeter (F) to regulate the flow of air through the apparatus, a mano- 
meter (G) to determine the resistance of the cartridge to the air flow, and 
a unit for sampling the air for chemical analyses. For the tests with 
parathion the unit shown in H with flowmeter £ is used, but for the 
chlorinated hydrocarbons the air is drawn through a heated quartz tube 
containing platinum foil to a glass absorption tower (not shown). Chamber 
A is a glass jar 16 inches in diameter and 30 inches high inverted on a 
small table in which two holes have been drilled. Into one hole (C_) is 
inserted a tube for injecting the dust or spray into the chamber, and in 
the other hole is a piece of 1/2-inch pipe(C') for connecting the cartridge 
holder. At the other outlet of the cartridge holder is another piece of 
1/2-inch pipe, which is connected by means of a street elbow and 21 -mm. 
(i.d.) glass tubing to the exposure chamber E, which is a 10-inch vacuum 
desiccator. From the top outlet of the exposure chamber extends glass 
tubing to the vacuum pump and the sampling unit, with the flowmeters 
and manometer inserted in series. 

The cartridge holder is shown in detail in figure 2. It was constructed 
from two floor flanges 4 1/4 inches in diameter made for 1 1/2-inch pipe 
(A and A'), and provided with gaskets (E and E'). The diameter of the 
outlets "was reduced to fit l/2-inch pipe by means of two 1 1/2- to 3/4-inch 
bushings (B and B*) and a 3/4- to 1/2-inch bushing (C). The cartridge (D) 
to be tested is placed between the pipe flanges, and the holder made air- 
tight with 1/4-inch bolts (_F). 



-3- 



Tests with Parathion. --For the tests with parathion dusts a wettable 
powder containing 15 percent of parathion in attapulgite clay was used, 
and for the test with sprays an emulsion containing 0.16 percent of 
parathion prepared from a 16 -percent emulsion concentrate. 

On the evening before a test was to be made portions of mite -infested 
leaves from the stock mite colonies were pinned to primary leaves on 
clean young lima bean plants with the upper surfaces together, and the 
tips and lobes of the bean leaves were cut off. The lima bean plants were 
placed under 200 -watt lamps. During the night the light and mild heat 
from the lamps stimulated the mites to move from the source leaf to the 
test leaf. Aphids were taken directly from the stock colony. 

In the morning, after the testing apparatus had been assembled, the 
test leaves infested with aphids and mites were removed from the plants, 
placed in vials containing water, and set in the exposure chamber (EJ. 
A petri dish was used under each vial to catch any insects that might fall 
from the leaves. Either 0.2 gram of the parathion dust or 1.4 grams of 
the emulsion was introduced into the chamber A every 5 minutes for 
15 minutes or 1 hour. For introducing the spray a hydraulic sprayer 
that produced a mist with an average particle size of 55-58 microns was 
used. These particles were found to settle at about the same rate as the 
dust particles. 

Air was drawn through the apparatus by means of a vacuum pump, at 
the rate of 16 liters per minute for cartridges for dual-type respirators 
and 32 liters for cartridges for single-type respirators. 

For chemical determinations samples of air were drawn through the 
sampling unit, which contained 5 ml. of absolute alcohol, at 1 liter per 
minute. At the end of the sampling time the alcohol from each unit was 
transferred to a volumetric flask, rinsed twice with 2 to 3 ml. of alcohol, 
and made up to 10. ml. with alcohol. The optical density was determined 
with a quartz spectrophotometer at a wave length of 274 millimicrons and 
compared with a previously prepared optical density-concentration curve 
(fig. 3). 

For the biological tests, after the exposure each leaf bearing aphids 
or mites was transferred to a vial standing in a beaker. A layer of 
paraffin in the beaker supported the vial and provided a light-colored 
surface on which fallen aphids or mites were readily observed, and a 
coating of lanolin on the rim prevented the survivors from escaping. 
Mortality counts of aphids were made after 4 to 6 hours. Affected 
individuals were shriveled, and a yellow exudate was usually present at 
the opening of the cornicles. Mites were usually examined at the same 
time, but always within 24 to 30 hours after they had been transferred to 
test leaves, to reduce the occurrence of newly hatched nymphs or new 
adults. Any that did appear were usually recognized by their lack of 
pigmentation. Aphids and mites that survived these tests were never 
returned to the stock colonies. 



4- 



Typical results obtained with parathion dusts are presented in table 1. 
Three types of cartridges were exposed to the dust-laden air in conjunction 
with the filters with which they would be used under practical conditions. 
The air was drawn through the apparatus at the rate of 16 liters per 
minute and the exposure period was 1 hour. 



Table 1. --Results of tests of three respirator cartridges against 15-percent 
parathion dust 



Cartridge 

type 



Weight of 
dust on 

cartridge 
filter 



Resistance of 
cartridge to 
air flow 



Initial 



Final 



Parathion passing 
through cartridge 



First 
10 min. 



Last 
10 min. 



Mortality of 
aphids after- 



First 
15 min. 



Last 
15 min. 



A 
B 
C 



Milligrams Inches of water Micrograms 



172 
185 
180 



0.5 
.4 
.5 



1.0 
.75 
.81 



0.45 
.50 
.35 



0.45 
.50 
.40 





Pe 


rcent 


61 




18 


35 




22 


42 




28 



Tests with Tetraethyl Pyrophosphate . --No chemical analysis was made 
to evaluate the amount of tetraethyl pyrophosphate passing through the 
cartridges, but only biological tests with aphids. The procedure was the 
same as for parathion, and the tests were made with a spray prepared 
by diluting a 38 to 40 percent emulsion concentrate (or wettable powder) 
to contain 1 part of tetraethyl pyrophosphate in 200 parts of water. 

In typical tests this spray was used on activated-charcoal cartridges 
in conjunction with two types of filters. Aphid mortalities determined 
after 60 minutes' exposure were as follows: 



Cartridge plus- 
Dust filter 
Fume filter 

Fume filter without cartridge 



Percent 

100, 99. 2, 99.3 
14.0, 10.4, 4.5 
12.9 



These results indicate that the dust filter in conjunction with an 
activated-charcoal cartridge will not remove tetraethyl pyrophosphate 
but that the fume filter is effective even without the cartridge. The 
fume filter is made to stop particles as small as 0.01 micron in diameter. 



-5- 



Tests with Chlorinated Hydrocarbon Insecticides. --Dieldrin was used 
both as a dust and as a spray, but aldrin and chlordane only as dusts. 
The concentration was 5 percent in all cases. The dieldrin and aldrin 
dusts were prepared by grinding the technical material with synthetic 
magnesium silicate, and the chlordane dust contained attapulgite clay as 
the diluent. The sprays were prepared from 25-percent emulsifiable con- 
centrates. The effectiveness of the cartridges was tested only by chemical 
analyses; no insect-mortality tests were made for these materials. 
Samples of air that had passed through the cartridges were drawn through 
the quartz tube containing platinum foil heated to a bright red to the absorp- 
tion tower containing glass beads that had been wet with a chlorine-free 
solution of sodium carbonate containing arsenic trioxide (1 gram of arsenic 
trioxide to 80 ml. of saturated sodium carbonate solution and 20 ml. of 
distilled water). At the end of the sampling period the beads were washed 
with distilled water. The washings were transferred to a Nessler tube, 
acidified with nitric acid, treated with an excess of silver nitrate, made 
up to volume, and the chlorine determined by the turbidimetric method. 

The results of typical tests with several respirator cartridges in 
conjunction with dust filters are shown in table 2. 

Table 2. --Results of tests of respirator cartridges with dust filters and 
of a fume filter alone against aldrin, dieldrin, and chlordane 



Type of cartridge 


Insecticide passing through cartridge 
(micrograms per liter) 


Dieldrin 


Aldrin 
dust 


Chlordane 




Dust 


Spray 


dust 



B 
C 

D 

Fume filter only 



0.4 


0.6 


.6 


.4 


.2 


- 


.4 


.8 


.2 


- 


.3 


.6 


1.1J/ 


- 


2.9 


3.6 


1.2 


- 



0.4 



.3 



0.3 



.3 

.3 
.3 



1/ In each of 3 replications. 



^•ss 1 — 



- 6 - 

Tests of Gas-Mask Canisters 

The apparatus for producing vapors for the testing of gas-mask 
canisters is shown in figure 4. Air is passed at the rate of 1/2 liter per 
minute through a fritted-glass bubbling unit (AJ and then through a column 
of glass beads (B) to remove small particles that might be carried in the 
air stream. The insecticide is allowed to drip into B from the separatory 
funnel (D) throughout the test period to keep the beads covered at all times. 
A small drying tube (C) removes the moisture from the air entering the 
funnel. The excess liquid is trapped in a flask (E). The outlet (_F) of the 
column is connected directly to the canister holder. The sampling unit 
and the insect-exposure chamber are the same as for the cartridge tests 
(fig. 1). To maintain a uniform temperature the entire apparatus is 
placed in a large constant-temperature box. All the tests reported were 
made at 85° F. 

Technical parathion, a product containing 38 to 40 percent of tetraethyl 
pyrophosphate, and technical tetraethyl dithiopyrophosphate were used to 
produce the vapors. 

The efficiency of the canisters was determined only by biological tests. 
The test insects were the same as for the tests of respirator cartridge. 

In tests of three commercial brands of canisters designed to remove 
organic vapors, acid gases, fumes, and dusts, an air stream containing 
60 micrograms of parathion vapor per liter gave 2, 1.7, and percent 
mortality after 60 minutes' exposure as compared with 100 percent 
mortality of aphids after 10 minutes' exposure to vapors that had not 
passed through a canister. 

Tests of similar canisters against tetraethyl pyrophosphate and 
tetraethyl dithiopyrophosphate vapors gave similar results. 

Summary 

Procedures have been developed for evaluating the efficiency of 
respirator cartridges in protecting against dusts and sprays of agricul- 
tural insecticides and of gas-mask canisters against vapors of these 
materials. These methods have been used to test cartridges and 
canisters for their effectiveness against parathion, tetraethyl pyro- 
phosphate, tetraethyl dithiopyrophosphate, aldrin, dieldrin, and 
chlordane. Results of some typical tests are presented. 

Literature Cited 

(1) Fulton, R. A. 

1950. How to select and use a respirator. Amer. Fruit Grower 
70(6): 17, 29. 

(2) Nelson, R. H. , and Smith, F. F. 

nF50. The toxicity of lindane vapor to insects. Jour. Econ. Ent. 
43: 223-224. 




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Figure 4. --Apparatus used for saturating air 
with organic phosphorus compounds. 



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